The increased maneuvering capability of present and future high-performance military aircraft imposes greater accelerations on the crew members than previous aircraft. These accelerations affect different portions of a pilot's body, particularly his head.
The pilot's head may be laterally displaced during a sharp turn or other flight maneuver. This may result in injury or make it difficult for the pilot to maintain his head in the proper position. Repeated lateral displacement of the pilot's head causes muscle strain and fatigue.
Many military aircraft include a "heads-up" display to provide instrument panel and weapons system information to the pilot. The information is electronically displayed and reflected into the pilot's view using various techniques and/or mirrors. Maintaining the proper head position is important for effective use of these display systems.
Lateral head displacement with the resultant problems sometimes occurs for racecar drivers. A solution used by racecar drivers is to attach a lanyard from their shoulders to the helmets to help react the lateral force on their heads resulting from the centripetal acceleration experienced in high-speed turns. This solution is not appropriate for aircraft pilots for numerous reasons. The aircraft pilot must have considerable freedom of movement to view the instrument panel as well as for checking aft and leaning forward.
European Patent No. 142,822 describes a padded headrest having sides that pivot about a point to swing against the passenger's head in the event the passenger's head is forced against a specific point on the back of the headrest. This type of headrest has the disadvantage of requiring the user's head to be in the correct position to trigger the device. British Patent No. 1,411,528, to Matthews, describes an inflatable cushion or pillow for use as a headrest. Such a headrest has many disadvantages, including not rapidly inflating nor serving to center the user's head during inflation. U.S. Pat. Nos. 3,218,103, to Boyce, and 3,953,049, to Surace et al., describe inflatable devices that, when in use, enclose the user's head. U.S. Pat. No. 3,645,259, to Schulman, describes an inflatable bag positioned beneath the pilot's chin which quickly inflates to a position between the chin and the chest of the pilot. U.S. Pat. No. 4,205,878, to Wooten, describes a seat with manually extendable headrests. U.S. Pat. No. 4,466,662, to McDonald et al., describes a headrest system for use in an aircraft. This headrest system is electrohydraulically actuated and controlled by the pilot in a variety of positions. This headrest has solid headrest pads 26 against which the back of the pilot's head rests.